I added the Ajax Control Toolkit and then an AutoExtender to my application. Now when I build, I get this message:

Indirect reference is being made to assembly System.Web.Extensions version 3.5.0.0, which contains 'AjaxControlToolkit.AutoCompleteExtender'. This Project references a prior version of System.Web.Extensions version 1.0.61025.0. To use 'AjaxControlToolkit.AutoCompleteExtender',
you must replace the reference to System.Web.Extensions with version 3.5.0.0 or higher.

I also get this:

Element 'AutoCompleteExtender' is not a known element. This can occur if there is a compilation error in the Web site.

in 3.5 they made (I think) all ofthe core ajax stuff part of the 3.5 install.

I don't recall right now if the toolkit is still valid or totaly replaced as of .net 3.5

as you have different bits trying to mix it's not working... make a new web and check the web config and fix the config.

Perhaps, but this is an ASP .Net 2.0 project. I'm working in VS 2005. I haven't updated yet, because some of the site is written using Monorail, and doesn't migrate to 3.5 very well. Untill I get all that working, I can't do 3.5... so just to get this little
bit working is all I'm after.

C:\Projects\IntranetApps\App_Code\BasePage.vb(264,0): warning BC42105: Function 'FormatDate' doesn't return a value on all code paths. A null reference exception could occur at run time when the result is used.

C:\Projects\IntranetApps\App_Code\FeedStats.vb(19,0): error BC30560: 'ScriptServiceAttribute' is ambiguous in the namespace 'System.Web.Script.Services'.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(12,0): error BC30560: 'UpdatePanel' is ambiguous in the namespace 'System.Web.UI'.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(31,0): error BC30560: 'UpdatePanelRenderMode' is ambiguous in the namespace 'System.Web.UI'.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(35,0): error BC30560: 'UpdatePanelRenderMode' is ambiguous in the namespace 'System.Web.UI'.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(51,0): error BC30284: sub 'RenderChildren' cannot be declared 'Overrides' because it does not override a sub in a base class.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(52,0): error BC30451: Name 'IsInPartialRendering' is not declared.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(62,0): error BC30451: Name 'ClientID' is not declared.

C:\Projects\IntranetApps\App_Code\PFBCUpdatePanel.vb(67,0): error BC30451: Name 'Controls' is not declared.